Barton Beds (now the Barton Group) is the name given to a series of grey and brown clays, with layers of sand, of Upper Eocene age (around 40 million years old), which are found in the Hampshire Basin of southern England. They are particularly well exposed in the cliffs at Barton-on-Sea, which is the world type locality for the Barton Beds, and lends its name to the Bartonian age of the Eocene epoch. The clay is abundant in fossils, especially molluscs.